In high volume manufacture of food products, particularly hamburger patties and other molded food products, it is frequently desirable to interleave the individual food products with separator sheets, usually paper sheets but sometimes plastic film or foil, and to stack the interleaved food products for packaging and shipment. In many high volume food product molding machines, such as the machines described in U.S. Pat. Nos. 3,887,964 and 4,054,967, the stacking and interleaving processes can be advantageously combined because the food products are discharged from the molding machine along a vertical path. Thus, the separator sheets can be projected into the vertical discharge path of the molding machine, the food products accumulating in interleaved stacks at the molding machine outlet. Effective and efficient paper interleaving and stacking devices of this kind are described in U.S. Pat. Nos. 3,675,387 and 3,952,478.
In some instances, however, it is desirable to carry out additional processing of hamburger patties or other food products, on an individual basis, after they have left the patty molding machine or other initial production equipment and prior to stacking. For example, it may be desirable to pass each food product through a cuber to form multiple depressions in the patty surface. In other instances, it may be desirable to add a layer of cheese or to apply seasoning or garnish ingredients to one surface of the patty. In systems of this kind, it is difficult to stack the food products accurately, particularly if separator sheets are applied to the individual food products as they leave the initial production machine.
The principal problem arises from the fact that virtually all stackers, other than those operating directly at the outlet of the molding machine, change the orientation of the food products to a substantial extent in the course of the stacking operation. Thus, in some stackers the food product is rotated through an angle of 180.degree. in the course of the stacking procedure. This almost inevitably leads to displacement of the separator sheets from the food products, and precludes effective controlled stacking. In other stackers, the patties or other food products may not be turned over completely, but they are tilted or otherwise changed in orientation enough so that accurate alignment of the separator sheets with the food products cannot be consistently maintained.